1. Field of the Invention
The present invention relates generally to production well systems, more specifically to assemblies and methods for achieving installation of a hanger in such systems.
2. Background of the Invention
Well fluid from a subsea well typically flows up a string of production tubing to a subsea wellhead. Sometimes well fluid is transmitted through a production riser to a Christmas tree on a vessel at the surface of the sea. It is often desirous however to transport the well fluid through a subsea Christmas tree to a collection facility or processing site.
In one type of subsea tree, the production tubing is suspended on a tubing hanger landed in a wellhead housing. The tree mounts to the wellhead housing and the tubing hanger has an axial through-bore to deliver fluid to the tree. The tubing hanger also has an annulus passage extending through it for communicating with the tubing annulus.
In another type, the tubing hanger lands in the tree, which is supported on the wellhead housing. The tubing hanger has a lateral port extending from it that aligns a lateral port in the tree.
In both of these types, the tubing hanger must be oriented, which can be complex in deep water. Also both types require relatively large diameters. To reduce expense, smaller diameter wells and components are desirable. Concentric tubing hangers do not require orientation. However, they typically require check valves for the annulus, thus historically are not used extensively.